(1) Field of the Invention
The present invention relates to a light emitting display apparatus of a top emission type, particularly to a technique to enhance visibility.
(2) Description of the Prior Art
In recent years, light emitting display apparatuses in which self-luminous devices are driven using thin-film transistors (hereinafter referred to as TFTs) attract attention, because of their ability to realize display apparatuses having high efficiency, high definition, low power consumption, and high-speed response. One type of such light emitting display apparatuses is top-emission organic electroluminescence panels (hereinafter referred to as organic EL panels), and vigorous researches are conducted on top-emission organic EL panels. In a top-emission organic EL panel, organic light emitting devices formed on a TFT substrate emit light. This light is emitted in a direction opposite to a direction through the substrate in which TFTS, wirings and the like are formed. As a result, the light is extracted from a “top” side of the panel highly efficiently.
This top-emission organic EL panel achieves color display in the following manner, as disclosed in Japanese patent application publication No. 2003-257622, for example. The organic light emitting devices emit white light to the “top” side. Color filters, which are provided in the direction of the light emission, selectively transmit and separate three primary colors composing the white light. Such a top-emission organic EL panel has advantages including a high luminous efficiency and a bright display on a screen, in addition to distinct features of general organic EL panels such as a thin panel and a wide viewing angle.
However, the top-emission organic EL panel has the following drawback. In the top-emission organic EL panel, an organic light emitting layer, which actually emits the light, is sandwiched between highly reflective layers. Therefore, the emitted light resonates, so that light of a particular wavelength is enhanced. Which is to say, a resonant structure is formed. Here, the resonant wavelength is different depending on an angle with respect to a direction perpendicular to a display unit of the panel. Accordingly, the color of the light emitted from the organic light emitting layer appears different for a user between when the user watches the display unit in the direction perpendicular to the display unit and when the user watches the display unit in a direction having an angle with respect to the perpendicular direction. This drawback is called color shifting.
In more detail, when the user watches the display unit of the light emitting display apparatus having a resonant structure in the direction having an angle with respect to the direction perpendicular to the display unit, a resonant wavelength in the direction in which the user watches the display unit is shifted to a shorter wavelength, in comparison with a resonant wavelength in the direction perpendicular to the display unit. In accordance with this change, a wavelength of light received by the user (hereinafter referred to as received light) is shifted to a shorter wavelength, and an intensity of the received light also changes. These changes cause color shifting.